Plasma and Fusion Research

Volume 16, 2402029 (2021)

Regular Articles

Measurement of Anisotropic Electron Velocity Distribution Function in LHD by Polarization Spectroscopy
Motoshi GOTO1,2), Nilam RAMAIYA3), Tetsutarou OISHI1,2), Yasuko KAWAMOTO1) and Tomoko KAWATE1,2,4)
1)
National Institute for Fusion Science, Toki 509-5292, Japan
2)
Department of Fusion Science, The Graduate University for Advanced Studies, SOKENDAI, Toki 509-5292, Japan
3)
Institute for Plasma Research, Gandhinagar 382428, India
4)
National Astronomical Observatory of Japan, Mitaka 181-8588, Japan
(Received 26 November 2020 / Accepted 27 January 2021 / Published 5 March 2021)

Abstract

Polarization of the hydrogen Lyman-α line is detected in the Large Helical Device. It is the first observation of a polarized atomic emission line in magnetically confined fusion plasma devices. With the help of an atomic model simulation, the anisotropy in the electron velocity distribution function (EVDF) in terms of T∥/T⊥ is evaluated, where T∥ and T⊥ represent the electron temperature in the parallel and perpendicular directions regarding the magnetic field, respectively. The results show that T∥/T⊥ has a tendency to decrease and deviate from unity with decreasing electron-electron collision frequency, which qualitatively agrees with an intuitive understanding of the anisotropic EVDF in the plasma boundary.

Keywords

plasma spectroscopy, polarization, Lyman-α, anisotropy, electron velocity distribution function

DOI: 10.1585/pfr.16.2402029

Full Text

PDF format (810Kbytes) PDF Download

References

  • [1] R. Makino et al., Plasma Fusion Res. 8, 2402115 (2013).
  • [2] V. Rozhansky, Contrib. Plasma Phys. 54, 508 (2014).
  • [3] R. Kano et al., Astrophys. J. Lett. 839, L10 (2017).
  • [4] R. Ishikawa et al., Astrophys. J. 841, 31 (2017).
  • [5] T. Fujimoto and A. Iwamae (ed), Plasma Polarization Spectroscopy (Springer, Berlin, 2008).
  • [6] I. Bray and A. Stelbovics, Adv. At. Mol. Opt. Phys. 35, 209 (1995).
  • [7] G.K. James, J.A. Slevin, D. Dziczek, J.W. McConkey and I. Bray, Phys. Rev. A 57, 1787 (1998).
  • [8] A. Hirabayashi, Y. Nambu, M. Hasuo and T. Fujimoto, Phys. Rev. A 37, 83 (1988).
  • [9] C. Stehlé and R. Hucheon, Astron. Astrophys. Suppl. Ser. 140, 93 (1999).
  • [10] A. Iwamae, M. Hayakawa, M. Atake, T. Fujimoto et al., Phys. Plasmas 12, 042501 (2005).
  • [11] A. Iwamae, A. Sakaue, N. Neshi, J. Yanagibayashi et al., J. Phys. B 43, 144019 (2010).
  • [12] M. Emoto et al., Fusion Eng. Des. 87, 2076 (2012).
  • [13] M. Goto and S. Morita, Plasma Fusion Res. 2, S1053 (2007).